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/*
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 * Copyright (c) 2011-2012, Stephen Colebourne & Michael Nascimento Santos
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  * Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
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 *  * Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
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 *  * Neither the name of JSR-310 nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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package java.time.format;

import static java.time.temporal.ChronoField.EPOCH_DAY;
import static java.time.temporal.ChronoField.INSTANT_SECONDS;
import static java.time.temporal.ChronoField.OFFSET_SECONDS;

import java.time.DateTimeException;
import java.time.Instant;
import java.time.ZoneId;
import java.time.ZoneOffset;
import java.time.chrono.ChronoLocalDate;
import java.time.chrono.Chronology;
import java.time.chrono.IsoChronology;
import java.time.temporal.ChronoField;
import java.time.temporal.TemporalAccessor;
import java.time.temporal.TemporalField;
import java.time.temporal.TemporalQueries;
import java.time.temporal.TemporalQuery;
import java.time.temporal.ValueRange;
import java.util.Locale;
import java.util.Objects;

/**
 * Context object used during date and time printing.
 * <p>
 * This class provides a single wrapper to items used in the format.
 *
 * @implSpec This class is a mutable context intended for use from a single thread. Usage of the
 * class is thread-safe within standard printing as the framework creates a new instance of the
 * class for each format and printing is single-threaded.
 * @since 1.8
 */
final class DateTimePrintContext {

  /**
   * The temporal being output.
   */
  private TemporalAccessor temporal;
  /**
   * The formatter, not null.
   */
  private DateTimeFormatter formatter;
  /**
   * Whether the current formatter is optional.
   */
  private int optional;

  /**
   * Creates a new instance of the context.
   *
   * @param temporal the temporal object being output, not null
   * @param formatter the formatter controlling the format, not null
   */
  DateTimePrintContext(TemporalAccessor temporal, DateTimeFormatter formatter) {
    super();
    this.temporal = adjust(temporal, formatter);
    this.formatter = formatter;
  }

  private static TemporalAccessor adjust(final TemporalAccessor temporal,
      DateTimeFormatter formatter) {
    // normal case first (early return is an optimization)
    Chronology overrideChrono = formatter.getChronology();
    ZoneId overrideZone = formatter.getZone();
    if (overrideChrono == null && overrideZone == null) {
      return temporal;
    }

    // ensure minimal change (early return is an optimization)
    Chronology temporalChrono = temporal.query(TemporalQueries.chronology());
    ZoneId temporalZone = temporal.query(TemporalQueries.zoneId());
    if (Objects.equals(overrideChrono, temporalChrono)) {
      overrideChrono = null;
    }
    if (Objects.equals(overrideZone, temporalZone)) {
      overrideZone = null;
    }
    if (overrideChrono == null && overrideZone == null) {
      return temporal;
    }

    // make adjustment
    final Chronology effectiveChrono = (overrideChrono != null ? overrideChrono : temporalChrono);
    if (overrideZone != null) {
      // if have zone and instant, calculation is simple, defaulting chrono if necessary
      if (temporal.isSupported(INSTANT_SECONDS)) {
        Chronology chrono = (effectiveChrono != null ? effectiveChrono : IsoChronology.INSTANCE);
        return chrono.zonedDateTime(Instant.from(temporal), overrideZone);
      }
      // block changing zone on OffsetTime, and similar problem cases
      if (overrideZone.normalized() instanceof ZoneOffset && temporal.isSupported(OFFSET_SECONDS) &&
          temporal.get(OFFSET_SECONDS) != overrideZone.getRules().getOffset(Instant.EPOCH)
              .getTotalSeconds()) {
        throw new DateTimeException("Unable to apply override zone '" + overrideZone +
            "' because the temporal object being formatted has a different offset but" +
            " does not represent an instant: " + temporal);
      }
    }
    final ZoneId effectiveZone = (overrideZone != null ? overrideZone : temporalZone);
    final ChronoLocalDate effectiveDate;
    if (overrideChrono != null) {
      if (temporal.isSupported(EPOCH_DAY)) {
        effectiveDate = effectiveChrono.date(temporal);
      } else {
        // check for date fields other than epoch-day, ignoring case of converting null to ISO
        if (!(overrideChrono == IsoChronology.INSTANCE && temporalChrono == null)) {
          for (ChronoField f : ChronoField.values()) {
            if (f.isDateBased() && temporal.isSupported(f)) {
              throw new DateTimeException("Unable to apply override chronology '" + overrideChrono +
                  "' because the temporal object being formatted contains date fields but" +
                  " does not represent a whole date: " + temporal);
            }
          }
        }
        effectiveDate = null;
      }
    } else {
      effectiveDate = null;
    }

    // combine available data
    // this is a non-standard temporal that is almost a pure delegate
    // this better handles map-like underlying temporal instances
    return new TemporalAccessor() {
      @Override
      public boolean isSupported(TemporalField field) {
        if (effectiveDate != null && field.isDateBased()) {
          return effectiveDate.isSupported(field);
        }
        return temporal.isSupported(field);
      }

      @Override
      public ValueRange range(TemporalField field) {
        if (effectiveDate != null && field.isDateBased()) {
          return effectiveDate.range(field);
        }
        return temporal.range(field);
      }

      @Override
      public long getLong(TemporalField field) {
        if (effectiveDate != null && field.isDateBased()) {
          return effectiveDate.getLong(field);
        }
        return temporal.getLong(field);
      }

      @SuppressWarnings("unchecked")
      @Override
      public <R> R query(TemporalQuery<R> query) {
        if (query == TemporalQueries.chronology()) {
          return (R) effectiveChrono;
        }
        if (query == TemporalQueries.zoneId()) {
          return (R) effectiveZone;
        }
        if (query == TemporalQueries.precision()) {
          return temporal.query(query);
        }
        return query.queryFrom(this);
      }
    };
  }

  //-----------------------------------------------------------------------

  /**
   * Gets the temporal object being output.
   *
   * @return the temporal object, not null
   */
  TemporalAccessor getTemporal() {
    return temporal;
  }

  /**
   * Gets the locale.
   * <p>
   * This locale is used to control localization in the format output except
   * where localization is controlled by the DecimalStyle.
   *
   * @return the locale, not null
   */
  Locale getLocale() {
    return formatter.getLocale();
  }

  /**
   * Gets the DecimalStyle.
   * <p>
   * The DecimalStyle controls the localization of numeric output.
   *
   * @return the DecimalStyle, not null
   */
  DecimalStyle getDecimalStyle() {
    return formatter.getDecimalStyle();
  }

  //-----------------------------------------------------------------------

  /**
   * Starts the printing of an optional segment of the input.
   */
  void startOptional() {
    this.optional++;
  }

  /**
   * Ends the printing of an optional segment of the input.
   */
  void endOptional() {
    this.optional--;
  }

  /**
   * Gets a value using a query.
   *
   * @param query the query to use, not null
   * @return the result, null if not found and optional is true
   * @throws DateTimeException if the type is not available and the section is not optional
   */
  <R> R getValue(TemporalQuery<R> query) {
    R result = temporal.query(query);
    if (result == null && optional == 0) {
      throw new DateTimeException("Unable to extract value: " + temporal.getClass());
    }
    return result;
  }

  /**
   * Gets the value of the specified field.
   * <p>
   * This will return the value for the specified field.
   *
   * @param field the field to find, not null
   * @return the value, null if not found and optional is true
   * @throws DateTimeException if the field is not available and the section is not optional
   */
  Long getValue(TemporalField field) {
    try {
      return temporal.getLong(field);
    } catch (DateTimeException ex) {
      if (optional > 0) {
        return null;
      }
      throw ex;
    }
  }

  //-----------------------------------------------------------------------

  /**
   * Returns a string version of the context for debugging.
   *
   * @return a string representation of the context, not null
   */
  @Override
  public String toString() {
    return temporal.toString();
  }

}
